Device for starting and feeding electric discharge tubes



Dec. 5, 1939. J. BETHENOD 2,132,609

DEVICE FOR STARTING AND FEEDING ELECTRIC DISCHARGE TUBES Filed Feb. 1, 1939 Patented Dec. 5, 1939 UNITED STATES PATENT OFFICE DEVICE FOR STARTING ANU FEEDING ELECTRIC DISCHARGE TUBES Application February ,1, 1939, Serial No. 253,978

In Switzerland August 9, 1938 2 Claims.

it is known to connect its electrodes to an alternating current supply through the intermediary of a reactance coil which ensures stable working conditions. The presence of the said coil diminishes the power factor of the installation, but the said factor can be easily made asnear unity as desired by means of a condenser connected across the terminals of the assembly formed 'by the tube and the reactance coil.

Such an installation necessitates the line voltage being sufilciently high to enable the tube to be started without dimculty. If this is not the case, more or less complicated starting devices must be provided, a known solution consisting in producing momentarily an over-voltage between the electrodes of the tube.

It is the aim of the present invention to provide a device of this kind, possessing the advantage of great simplicity, the over-voltage being obtained without the necessity of adding supplementary members to the installation which are rendered inoperative after the starting. According to the invention a circuit consisting of two reactance coils coupled in series with a condenser is connected across the feed supply terminals, the tube being connected to the terminals of the assembly formed by one of the reactance coils and the condenser, a switch being provided for connecting the two reactance coils in parallel as soon as the starting of the tube has been effected.

' The drawing shows by way of non-'limitative example a diagram of the installation according to the present invention.

In the drawing I represents a luminescent discharge tube, 2 and 3 reactance coils, 4 a condenser, a switch, the voltage of the feed line being applied at I.

On considering in the first place the functioning of this assembly when the tube is lighted, the switch 5 being closed, the inductances 2 and l coupled in parallel ensure the stability of the working voltage and the condenser 4 raises the power factor of the installation as mentioned above. On the other hand, when the tube is extinguished, it suiilces to open the switch 5 in order to constitute, by means of the reactance coils 2 and 8 and the condenser 4, an oscillating circuit connected across the terminals U of the supply line: a resonance effect is then produced owing to which the voltage at the terminals of adjusted within certain limits.

For the feeding of an electric discharge tube the assembly 2, 4 may be much higher than the line voltage, and the tube starts. Moreover, experience shows that a suitable resonance effect may be obtained by so dimensioning the reactance coils 2 and 3 and the condenser 4 as to obtain the 6 best working once the tube is lighted. The cl I ation of the over-voltage necessary for staring being very limited, the opening of the auxiiiary switch 5 may be efiected by means of a push button especially when the general switch of the in- 10 stallation (not shown) comprises a control of this kind. In these circumstances the mechanism of the said two switches may be easily combined so as to ensure the starting of the tube at the closing-of the principal switch without the operator having to carry out any supplementary operation. The opening of the switch 5 may alternatively be effected by means of a relay actuated by the feed current of the tube, and there are numerous ways of carrying this into eflect.

Finally a certain amount of mutual induction between the reactance coils 2 and 3 may be provided for, by partially combining in known manner their magnetic circuits; thus for a given value of the equivalent reactance of the said coils 5 coupled in parallel by the closing of the switch 5, the reactance of the oscillating starting circuit produced by the opening of the switch 5 may be This, if necessary, allows a suitable over-voltage to be produced at the moment of starting, without the necessity of modifying the values of the various constants chosen for the best possible functioning of the installation, once the starting has been effected.

WhatI claim is:

1. A device for starting and feeding an electric discharge tube by means of analternating current supply, which comprises a circuit consisting of two reactance coils coupled in series with a condenser and connected across the terminals of 40 the said supply, the tube being connectedacross the terminals of the assembly formed by one of the reactance coils and the condenser, and a switch being provided for connecting the two reactance coils in parallel as soon as the start- 4 ing of the tube has been effected;

2. A device according to claim 1 in which the two. reactance coils are arranged so as to produce a certain amount of mutual inductance between them.

' JOSEPH sermon. 

